Condom Broke; Needing Insight!

Hello! So my boyfriend and I were having sex tonight and he had a condom on, but while we were getting down and dirty he felt something popped and immediately pulled out to find the condom had split at the tip. I'm really concerned about him being exposed inside of me, even for a split second, and the typical initial fear of pregnancy. He didn't cum at all, but we were unsure about the chance of precum and it completely killed the mood for me and I've been terrified on what to do. I was suppose to start my period today and it didn't happen, so I still have that to cling to but I'm not quite sure what to do to make sure nothing swam through. I'm a tad paranoid and I really need some advice or reassurance from fellow experienced females. I looked into the Plan B One Step and even a pregnancy test, but the Plan B was godly expensive and the test would determine too late if something did happen. What should I do?